How to solve the problem that "w5500 chip cannot connect to the server immediately after power failure and restart in tcp_client mode"

Q:  Chip in TCP_Client In mode , Unable to connect to the server immediately after power failure and restart

R:  This is because the client does not actively send a disconnect request , Cause the server doesn't know Socket Abnormal disconnection has occurred ; After power on again , Chips in the same IP And port to the server , And the server also thinks this Socket Links exist , So reject the immediate connection of the chip .

A:  Solution ：

In chip use KEEP_ALIVE Mechanism , Send breathing packets for a period of time , If the chip does not reply to the server , The server judges that the link is broken , And release Socket resources , Then you can successfully connect . If there is no requirement for the local port of the client , You can also initialize Socket The part of makes the port automatically +1 Handle . The two methods are adopted according to the specific application analysis .

notes : Some scenarios cannot use port Automation +1 The way , Like electricity 104 Statute , Only 2404 Port connection .

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